全文获取类型
收费全文 | 148475篇 |
免费 | 13229篇 |
国内免费 | 7720篇 |
专业分类
化学 | 73663篇 |
晶体学 | 1398篇 |
力学 | 11177篇 |
综合类 | 325篇 |
数学 | 39505篇 |
物理学 | 43356篇 |
出版年
2024年 | 282篇 |
2023年 | 1618篇 |
2022年 | 2758篇 |
2021年 | 2784篇 |
2020年 | 3144篇 |
2019年 | 2946篇 |
2018年 | 12336篇 |
2017年 | 11984篇 |
2016年 | 9290篇 |
2015年 | 4319篇 |
2014年 | 4478篇 |
2013年 | 5663篇 |
2012年 | 10402篇 |
2011年 | 16818篇 |
2010年 | 9917篇 |
2009年 | 10037篇 |
2008年 | 10958篇 |
2007年 | 12605篇 |
2006年 | 4024篇 |
2005年 | 4438篇 |
2004年 | 3931篇 |
2003年 | 3839篇 |
2002年 | 2735篇 |
2001年 | 1722篇 |
2000年 | 1654篇 |
1999年 | 1715篇 |
1998年 | 1508篇 |
1997年 | 1444篇 |
1996年 | 1494篇 |
1995年 | 1173篇 |
1994年 | 999篇 |
1993年 | 864篇 |
1992年 | 732篇 |
1991年 | 643篇 |
1990年 | 554篇 |
1989年 | 445篇 |
1988年 | 394篇 |
1987年 | 331篇 |
1986年 | 309篇 |
1985年 | 252篇 |
1984年 | 185篇 |
1983年 | 138篇 |
1982年 | 121篇 |
1981年 | 105篇 |
1980年 | 111篇 |
1979年 | 76篇 |
1978年 | 64篇 |
1977年 | 58篇 |
1976年 | 46篇 |
1973年 | 53篇 |
排序方式: 共有10000条查询结果,搜索用时 343 毫秒
961.
本文提出一种利用材料Hugoniot数据研究高压下离子晶体中微观离子状态及其离子间排斥作用势的新方法。对氢化锂晶体进行研究时,我们得到Li~+和H~-离子之间排斥作用势函数,结果表明文献〔1〕中提出的离子压缩效应具有客观性。 相似文献
962.
H-空间与拟向量变分不等式 总被引:2,自引:0,他引:2
本在Hausdorff locally convex H-空间上建立了一个新的不动点定理;利用局部交性质,在Hausdorff locally convex H-空间上建立了相应的拟向量变分不等式. 相似文献
963.
Conductivity, viscosity, turbidity, and NMR measurements were performed over most of the mole fraction range for sodium deoxycholate (SDC) with hexadecyltrimethylammonium bromide (HTAB), hexadecylpyridinium bromide (HPyBr), and hexadecylpyridinium chloride (HPyCl). All studies demonstrate that the mixed-micelle formation is more favorable in SDC plus HTAB rather than SDC plus HPyBr or SDC plus HPyCl mixtures. The results showed that the bulky pyridinium head groups of HPyBr or HPyCl create steric incompatibility with rigid SDC monomers in the mixed state. 相似文献
964.
电磁继电器触点参数的测试 总被引:1,自引:0,他引:1
本文介绍了电磁继电器触点电参数的测试方法,包括接触电阻、绝缘电阻参数测试。 相似文献
965.
Miroslav Ploščica 《Algebra Universalis》2003,49(1):1-12
966.
967.
A new collectively fixed point theorem for a family of set-valued mappings defined on product spaces of non-compact topological spaces without linear structure is proved and some special cases are also discussed. As applications, some non-empty intersection theorems of sets with convex sections and equilibrium existence theorem of abstract economies are obtained under much weaker assumptions. Our results includes a number of known results as many special cases. 相似文献
968.
ZhengBin Zhang Chunying Liu Peifeng Li Zhenzhen Wu Cai Lin Huawei Huang Lei Xing Liansheng Liu 《Frontiers of Chemistry in China》2006,1(1):86-97
Many food algae and red tide algae were cultivated in the f/2 medium, and the nitric oxide (NO) concentration of the medium
and the cell density were determined. The experiments on algae were conducted when different concentrations of NO were added
into the medium using two methods. The results show that low concentrations of NO were self-produced by marine algae during
the exponential growth period and were about nmol/L level. But at the end of the period, i.e., 2 or 3 days before the cell
density reaches the maximum, an NO peak appeared, with the NO concentration reaching 10 nmol/L. The NO threshold concentration
exists according to the influence of exogenous NO on the marine phytoplankton growth. One type is the threshold concentration
that can promote algae growth, and its value is between 10 and 1 nmol level, or even lower. The other type can inhibit the
phytoplankton growth, which is about μmol level or higher. The results indicate that red tide algae are far more sensitive
to NO than are food algae. The fundamental experimental outcome above may provide a new clue for red tide chemical forecast
by inspecting the NO change. 相似文献
969.
970.
§1 IntroductionAt present,boundary value problems (BVPs) are widely investigated with variousmethods and techniques. BVPs with integral boundary conditions constitute a veryinteresting class of problems such as multipoint,three-point,four-point and nonlocalboundary value problems which are considered by many authors.And the existence ofpositive solutions for these problems becomes the subjectof many papers[1—6] .In a recentpaper[7] ,the authors have studied the existence of positive solut… 相似文献